Researchers Discover Compounds that Inhibit Cryptosporidium

Cryptosporidium parvum is a tiny yet insidious waterborne parasite that wreaks havoc worldwide. Cryptosporidium is resistant to water chlorination and has caused outbreaks in the U.S., leading to the concern that the parasite could be used as a bioterrorism agent. There are neither vaccines nor effective drugs available to respond to these multiple threats to human health.

In this week’s issue of Chemical Biology, researchers at Brandeis University and the University of Georgia report they have identified lead compounds that inhibit Cryptosporidium’s parasitic punch, paving the way for an effective antibiotic treatment. In all, scientists identified ten new compounds, four of which are better at fighting Cryptosporidium than the antibiotic paromomycin, the current gold standard for evaluating anticryptosporidial activity.

“These are promising new compounds and this research provides an avenue of much needed therapy for this disease,” said Brandeis biochemist Lizbeth Hedstrom, whose lab identified the compounds together with parasitologist Boris Striepen of the University of Georgia.

While there are many drugs to treat bacterial infections, it has been very difficult to find drugs against pathogens like Cryptosporidium because the proteins of these parasites are very similar to those of their human host. Scientists have been further thwarted because little was known about Cryptosporidium metabolism. This situation recently changed dramatically when genome sequencing provided a genetic blueprint of the bacteria.

In work leading up to the current study, Hedstrom and Striepen used this blueprint to show that Cryptosporidium has a very simple process to produce the building blocks of DNA and RNA. Surprisingly, the researchers also discovered that the bacteria stole a critical gene in this pathway from intestinal bacteria. This unusually large evolutionary divergence between parasite and host proteins provides an unexpected platform for novel drug design.

“The quest to develop drugs to treat this debilitating disease has been almost futile,” said Hedstrom. “We are still a long way from an actual anticryptosporidial drug, but we are very encouraged by these results.”